I agree with you about dogs - my dog clearly has a memory, too. I tried to find something useful for you by searching at www.google.com but my words - memory, brain, human, dog (or animal) gave me mostly just things that seemed to be news notes where one news item would be about memory and one about dogs, for example, or where the 'dog' was just an image in the mind of the human.

So I'll just tell you what I can:

Memory is still a very complicated question. Once scientists trained worms and then ground them up and fed them to untrained worms. They thought the untrained worms learned faster after eating the trained worms. But it looks like that must have been bad research, because I don't hear about it any more. Also, they think our brains were like a hologram: if you explore any part of your brain, your memories are fuzzier, but they're not lost, so there's not a single 'memory' region of the brain.

My text book has pictures of human and cat brains that show how the higher brain - the cerebrum - is much larger in human than cat and has lots more ridges on it. It says birds and mammals have big brains compared with lower animals. (My cockatoo could learn and remember.)

I bought pig brains for a science lab from a grocery store in Virginia one year, and they were like white lumps of lard or butter, but with some ridges. It was amazing how fatty they were, to insulate all the electric signals that run from one nerve cell to another. Good luck!